Existing methods for dual-energy or spectral tomography include, for example, fast kVp switching of a single source during rotation, multiple rotations of a single source (varying the kVp in each rotation); detector configurations providing energy discrimination in the detected signal (e.g., energy-discriminating photon counters or sandwich detectors); two (or more) x-ray sources each used in combination with a detector (e.g. a dual-source CT scanner involving two x-ray sources and two detectors); and most recently in development, a configuration of x-ray sources distributed in the axial plane (i.e. in the x direction orthogonal to the axis of rotation) and a single detector. However, none of the existing methods for dual-energy (or spectral) imaging configure x-ray sources along the z-direction, and therefore result in images with a shortened longitudinal field of view and higher incidence of cone-beam artifacts.
Accordingly, there is a need in the art for a method of dual-energy imaging with x-ray sources configured along the z-direction, in order to extend longitudinal field of view and reduction of cone-beam artifacts.